Case studies on process monitoring

4.2.1. Deployment of a wireless sensor network for process measurement in the Fast Breeder Test Reactor at the Indira Gandhi Centre for Atomic Research, India

The Fast Breeder Test Reactor is a 40 MW(th) sodium cooled fast reactor built at the Indira Gandhi Centre for Atomic Research, in Kalpakkam, India. In the reactor, WSNs have been deployed to test the feasibility of such networks in industrial and nuclear installations.

During initial deployment in 2010, eight temperature sensors and three vibration sensors were connected to WSN nodes. These sensors were distributed outside the reactor containment building, the turbine building, the secondary sodium loop area, the sodium flooding area and a speed control system and blower cabin in the filter room. Three router nodes were used to route these signals towards the base station placed in the control room.

To ensure continuous availability of all the nodes in the network, battery backup has been provided. Diverse process signals (such as temperature, flow, level and vibration), sometimes grouped together in a nearby location, have to be monitored. Different types of sensor acquisition boards, capable of handling multiple input channels, have been designed and developed.

As of 2017, the Fast Breeder Test Reactor WSN is functioning satisfactorily with 37 nodes. It monitors 14 thermocouples, six flow sensors, two level sensors, five vibration sensors and two vibration based condition monitoring systems. To administer and manage the WSN, an efficient graphical user interface wireless network management station has been developed. Figure 5 shows the deployed WSN at the Fast Breeder Test Reactor.

FIG. 5. Deployed wireless sensor network at the Fast Breeder Test Reactor.

4.2.2. Deployment of wireless sensor network for the measurement of sodium leak detection at the In Sodium Test Facility, Indira Gandhi Centre for Atomic Research, India

The In Sodium Test Facility was constructed at the Indira Gandhi Centre for Atomic Research to test the mechanical properties of fast reactor components under the influence of sodium. Molten sodium is circulated in the heat transport circuits of the fast breeder reactors and experimental sodium loops at the centre. The material used for these sodium circuits is austenitic stainless steel with a welded construction. The possibility of a leak cannot be completely ruled out, even though all possible measures are taken to prevent sodium leaks by adequate design, fabrication, quality assurance, operation and maintenance. Wire type leak detectors and spark plug type leak detectors are used as the primary leak detection method in single wall pipelines of secondary sodium circuits and experimental loops. The wire type and spark plug type leak detectors are connected to programmable logic controllers to process the signal from the detectors.

In order to reduce the complexity involved in cable routing and to test the performance of the leak detector wireless connectivity, 50 leak detectors from the In Sodium Test Facility fatigue loop were connected as a redundant system in parallel mode to a WSN developed in house. The data were communicated to a base station located in the control room to display the status of the leak detectors.

Prior to deployment, interference effect studies were performed using a spectrum analyser to identify any sources of interference. Typical WSN sensor node installations are shown in Fig. 6.

The network was distributed across three floors of the building, covering a nearly 80 m² area. Three router nodes were placed on each floor to provide a redundant path. The base station was connected to a personal computer and received the field data from the sensor nodes. The statuses of the leak detectors were displayed on the computer. An actuator node for a buzzer alarm in case of sodium leak was installed in the control room.

4.2.3. Deployment of wireless sensor network for the measurement of temperature and humidity at the Safety Grade Decay Heat Removal Loop in Natrium, Indira Gandhi Centre for Atomic Research, India

The Safety Grade Decay Heat Removal Loop in Natrium facility at the Indira Gandhi Centre for Atomic Research is a 335 kW sodium test facility used to study the safety grade decay heat removal of the Prototype Fast Breeder Reactor. A ventilation stack 20 m in height provides the air flow required to transfer the heat from the secondary sodium circuit to the atmosphere through an air heat exchanger.

When the loop is in operation, it is necessary to continuously monitor the temperature and humidity at the stack inlet and outlet from the control room. Wiring the facility over a long distance was considered cumbersome

FIG. 6. Deployed wireless sensor nodes at In Sodium Test Facility.

and a WSN based solution was determined to be the most appropriate. The links were established for continuous data monitoring at 1 min intervals at 2.4 GHz.

The WSN was deployed using five nodes between an open terrace and the control room, as shown in Fig. 7.

The parameters from the ventilation stack inlet and outlet were acquired, processed and transmitted successfully to the control room. The connection status of two temperature and two humidity sensors to the WSN nodes was verified on a regular basis.

FIG. 7. Wireless sensor network (WSN) deployed at the Safety Grade Decay Heat Removal Loop in Natrium facility.